That's the basic premise of index funds.

Presumably when they vote, their interest will be in seeing the entire index go up, not one company stealing the market share of another.

When supply chain disruptions during COVID caused significant supply shortages, companies raised prices as one would expect due to the classical law of supply and demand.

By the time those shortages ended, there was so much media buzz about inflation that those companies realized, independently, that they could probably keep prices high and no one would notice.

They did this. It worked. The media still kept talking about inflation. Wages started to recover a little bit from the beating they took during the pandemic, and the Fed started talking about forcing wages down to fight inflation.

Those companies, independently, saw this and broke out in the biggest shit-eating grins ever. They raised prices again, purely to juice their profits, and still the media and Fed were only talking about inflation as if it was caused by wages.

Only now, months/years later (depending on where you start counting), is the media starting to catch up to what's actually been happening.

(And I'm sure that it's also something of an oversimplification—that the inflation hasn't been caused solely by this corporate greed. But I'm pretty damn sure that in this instance, it has been caused primarily by corporate greed.)

TL;DR: Active collusion is not necessary in a situation where multiple actors within the system can independently recognize actions that will benefit them at others' expense, and engage in them simultaneously. It is a zeitgeist, or possibly a bellwether and then flock movement, not conspiracy.